Lens protractor



April 7, 192 5. 7 1,532,878

L. BUGBEE LENS PROTRACTOR Filed July 12, 1923 uumn l I:

A TTORNEYS.

/MM v Patented Apr. 7, 1925,

UNITED STATES PATENT- rice;

LUCIAN w. BUGBEE, or innraimronis, mnmnanssrenon ro oimrincn BIFOGAI I LENS COMPANY, or INDIANEiEQLIS,INDIANA, A CORPORATION.

LENS PROTR-AGTOR.

Application filed July 12,

Z '0 aZZwho-m it may concern:

Be it known that I, LUGIAN W. BUGBEE, a citizen of the United States, and a resident of Indianapolis, county of Marion, and State of Indiana, have invented a certain new and useful Lens Protractoryand I do hereby declare that the following is a full, clear, and exact description thereof,

of the protractor which-"constitutes this in-' vention.- Fig. 2 is a *diarnetricalz'cross'secitionthereo'f. P 7 .s

' Fig. 3 is a central vertical section through a; one piece bifocal-lens blank before" it is reference being had tothe accompanying drawings, in which like numerals refer to like parts.

The object of this invention is to provide an efficient and satisfactory protractor for. use in locating the axes of bifocal lenses, and especially in making one piece bifocal: lenses, for centering and decentering' the same and locating the meridians of the lens for aid in scientifically finishing the prescription side thereof or the side opposite the bifocal side thereof and for edgingand otherwise forming and mounting the lens accurately in'the fixed position.

This invention is of special value foruse in the proper manufacture and finishing- 0f. bifocal lenses, and especially a one piece bifocal lens or lens blank having a division line between the bifocal, surfaces. =Oorresponding division'lines are marked on the protractor and the proper location of the lens is determined by the division line. That is, the bifocal lens is placed on the protractor so that the division'line of the lens will register with the division 'line shown in the protractor. The remaining characteristics of the lens are then deter mined and marked with reference to thel reading segment which is enclosed by said' division line. This will enable one to propcrly center or decentcr the lens, for aid in finishing properly the prescription side, and in locating the axis of the cylinders by i the meridian lines and the corresponding thicknesses of the lens near the/edge at several points for the proper edging and mounting of" the lens. 1 1

Making the protractor of glass 01 other transparent material, so that light will pass through the p-rotractor such lenses'or lens blanks thereon enables oneto quickly and accurately locate the lines andnunierals of the chart and mark the lens accordingly. l/Vith paper chart or other opaque protractor, it is very diflicult or impossible to seeand locate thedivision line of the lens 1923. Serial No. 651,075..-

The fullnature of the invention wil-l' be understood from the 1 accompanying drawings and the following. description and In the "drawings, Figure 1 isa' plan view finished-on. the prescription'fside. f Fig. 4

is a central vertical section throu'gh'a-one-- PIGCGblfOCfil lens after it has been finished on' the prescription side, the dottediline hasfbeen removed in finishing "the'same. Fig. 51s a y This protractor is a plate or disk 10 made of glass or other transparent material. Upon one side thereof a 'chartof lines and numerals are'placed', the 'same as in paper protractors, andathese may be such asdez sired. In 'the drawings there is indicated a circle 11 concentric of-the disk lO-fa'nd having the two primaryfmeridian lines 12 and 13 traversing the' same; From the circle 11 radial lines iltfai-e indicated representing various 'degrees of a circle and these degrees are indicated by the numerals 15, so thatreach end of the meridian 'line'12 is marked" 180 and each end-of the primary meridian line 13- is marked 9O 1; 1

'On eachprimarymeridian line 12 and 13 there is a 'inillimeter 'scale'16 and the millip iew of the bifocal side of the lens. v

indicating the portion of the, blank thatj ineter scale in the lower half extends from reading fieldsjin bifocal lenses:

. In centering a bifocal lens or one piece bifocal lens blank preliminary to finishing the prescription side'and 'edging andfinally shaping of the lens, the bifocal lens blank is placed on the protractor so that the division line between the bifocal surfaces will register with one of the curved lines 18,

19 and 20, and then the various centers and other points on the lens blank are marked by ink with'a pen in accordance with the lines on the protractor'and in the manner hereafter more fully explained.

WVith the protractor formed of glass or transparent materiah'the protractor with 'the' lens blankthereon can be held up to the light and thus render it a very easy and quick operation for the workmen to see the division line in the lens and be sure that.

it registers exactly with the corresponding line on the protracton, Heretofore, as stated'above, when opaque protractors have been employed, it has been diflicult to see the division line in the lens and place the blank so that the division lin'e'of the lens and the corresponding line of the protractor register with each other. This has always caused confusion and often loss of time;

Inorderv to scientifically and properly finish theprescription-side ofa onepiece bifocal lens, it is necessary to pay attention to the location of the optical centers of. the

lens and of the'two bifocal surfaces and also the proper meridian for the cylinder axis. This is all the more necessary and is ren-v dered additionally difficult by the fact that 'the reading field of the blank is l thicker ground and particularly. being at" the tical centers are at the thickest portion of" than: therest of the lens'on account ofthe longer radius of the curvature of the reading field inithe usual form of such lenses. 1Therefore, in locating the optical centersof the lens, it is necessary to keep awayv from this thickened portion or rather to make proper allowance forit.

. As seen in Fig; 3, the optical center is at the lower edge of the blank 25, being the center of the two bifocal surfaces as thickest portion ofv the lens. After the blankhas been-finished on the bifocal side,

there is no optical center at the low'er edge,

of the finished lens 27,but instead there are two opticalcentersfone for each field," the upper one for the distance fieldand'the lower one for-the reading field; These opeach of the two fields and the prescription side should b'e s0 surfaced that the optical i' center of each field will be in line with the usual c'enterof vision through each field so as to make the same comfortable to the eye. Fig. 5 is a plan view of the bifocal side and shows the two optical centers 28 and 29, one above and the other below-the division line 30 between thetwo fields.

The actual process of centering such onepiece bifocal lens isas follo'wsz.

'The lens blank 's located/so that the division line between the two bifocal surfaces register with one ofthe curved lines 18, 19 and-20, the optical center'would'be at the point where the two primarymeridianiliiies intersect if the major or distance portion of the lens had no power, but the prescription of the lens in which the reading field has primary meridian 13.

the optical center dot.

some-power as indicated in the prescription and the optical center therefore will be on the primary meridian line 13 at a certain number of milllmeters above thehorizontal primary meridian line 12 according to the power of said distance v field and at that point a dot is made on the lens blank which finished if no allowance is made for insetting.

the reading field. But it is the'better prac tice and iscustomary for the reading field to be inset and that is determinedby 1 the prescription and, therefore, the blank is turned on the protracto-r so as to bring the center of the reading field a certain number 7 of millimeters to one side of the vertical v The millimeter lines 17 inthe protractor indicate the extent of this insetting of the reading field. Then dots are made on the glassindicating the optical center of the reading-field, and the meridian lines so as to indicate the position indicates the optical center of the lens when I of theaxis of the cylinder, and four dots are placed on the outer portions of the; blankf about equal distance apart for use in'measuringthe edge thickness of the lens, these dots being equidistant from the dotmarking the required positionv of the oprtical center. f

After thelens blank has been thus marked with the protractor, itis ground on the pre- 1 scription side to form theprescription surlens willbe inthe. proper. meridian and so :that the thickness of the lens at'the diagonally opposite measuring points will be exactly the same and equally spaced from The four thickness measuring pointsmust be dotted only on the distance field of the blank and never on the face and so that the'c'ylinder axis of the r reading-field as the latt er is thicker than the 7 sary.

The invention claimed .is

1. A 'protractor for use in making bifocal lenses formed of transparent material, and chart linesand numerals placed thereon including curved lines adapted to register with the division line between the bifocal surfaces of bifocal lenses or lens blanks.

2. A protractor for use in making bifocal lenses including a glass plate, and chart lines and numerals placed 011 said plate including equatorial. and meridonal primary merldian lines, a circle concentric with their intersec- L bisected by the meridonal line, and millimeter scales adjacent said primary meridian lines, substantially as set forth;

3. A protractor for use in making bifocal lenses including a glass plate, concavo-con- 2 vex, chart lines and numerals placed thereon, including curved lines adapted to reg ister with the division line between the b-i-' focal surfaces of bifocal lens or lens blanks, and more than two lugs secured on the glass equidistant from each other and the center of the protractor for supporting the lens or lens blank.

In witness whereof, I have hereunto affixed my signature. v V

LUCIAN W. BUGBEE. 

